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This invention relates generally to coolant recirculation systems and, more particularly, to apparatus and methods for monitoring, characterizing, and testing coolant recirculation systems.
Various industries, including the semiconductor manufacturing facilities, general manufacturing industries, and military organizations, regularly utilize cooling systems with heat exchangers and recirculating coolant. In these industries and elsewhere, such recirculating-coolant heat-exchanger cooling systems are used to remove excess heat in naval vessels, manufacturing process equipment, HVAC installations, etc. Expensive failures of these systems can be the result of many factors, including fouling, inadequate flow, and excessive heat load. When a need occurs to provide for cooling new equipment or to add additional equipment load onto an existing cooling system, there is often uncertainty as to the actual heat removal capacity and reliability of the proposed new system or the existing system. Thus there is a need for apparatus and methods for consistent, reproducible, quantitative testing and characterization of coolant recirculation systems.
U.S. Pat. No. 4,201,518 to Stevenson discloses a recirculating hot-water pump control system.
U.S. Pat. No. 3,593,578 to Farrell et al. discloses an apparatus for measuring the amount of heat absorbed or given up by a heat-transferring structure such as a heat exchanger. The apparatus comprises a wheel-and-disc type integrator having a disc coupled to a volumetric flowmeter output shaft and a wheel positionable on the disk by a dual bellows assembly which measures the inlet and outlet temperatures of the heat exchanger. A differential mechanism has an output drive connected to a counter for totalizing the amount of heat transferred relative to the heat exchanger.
U.S. Pat. No. 3,631,717 to Kato et al. discloses a calorie-measuring device comprising a flowmeter arranged in a pipeline through which a heat carrier flows to a load wherein heat is emitted or absorbed. A device provides a signal indicative of difference between temperatures before and after the load, and a further device serves for multiplying the values of flow quantity and temperature difference to indicate the caloric value of heat emitted or absorbed in the load.
U.S. Pat. No. 3,918,300 to Weisstuch et al. discloses a device for measuring the efficiency of a heat exchanger. The device comprises a plurality of temperature sensors, a plurality of difference means, and calculation means which generates a signal representative of the efficiency of the heat exchanger, either the heat transfer coefficient or the fouling factor in the heat exchanger.
U.S. Pat. No. 4,024,751 to Potrzebowski discloses an apparatus for determining heat transfer efficiency of a heat exchanger wall, comprising means for imposing a heat load on a first heat transfer surface of the wall and means for determining the rate of dissipation of the heat load across the wall and into a heat exchange fluid in contact with a second heat transfer surface of the wall.
U.S. Pat. No. 4,479,727 to Domingorena et al. discloses a method and apparatus for evaluating the performance of a heat exchanger, in which water is supplied to the heat exchanger at a known mass flow rate and temperature. The water is directed to traverse a flow path of the heat exchanger. The water is then heated and redirected into another flow path of the heat exchanger in heat exchange relation with the first flow path. The temperature change of the water over a flow path is measured to determine the performance of the heat exchange.
U.S. Pat. No. 4,729,667 to Blangetti et al. discloses a process and device for the determination of the thermal resistance of contaminated heat exchange elements of thermodynamic apparatuses, in particular of power station condensers, using two comparison tube sections which originate from a single condenser tube and of which one is left in the corroded condition and/or the condition encrusted by mineral deposits and the other is brought into the new condition by etching or other cleaning procedures. The two comparison tube sections are conductively connected in series, cooling water flows through them, and they are heated from the outside in a condenser chamber in each case by steam flows of equal power. The temperatures measured at the inlet and outlet positions of the comparison tube sections, the measured values of the mass flow of cooling water, the steam temperatures, and the heat flows in the two condenser chambers permit the determination of the thermal resistance of the incrustation layer of the tube drawn for the purposes of investigation from the condenser. A device for carrying out the process is also described.
U.S. Pat. No. 4,766,553 to Kaya et al. discloses a heat exchanger performance monitor which generates a fouling factor which indicates the level of fouling of a heat exchanger having a heat exchange surface area and through which a heat exchange medium passes having a known specific heat. Temperature transmitters are utilized to obtain values for the input and output temperatures of the heat exchange medium as well as the temperature in the heat exchanger of a heat exchange fluid used to transfer heat to or from the heat exchange medium. Modules are used to generate a value for an actual heat transfer coefficient in the heat exchanger as a function of the temperatures, flow rate, and constant parameters such as area and specific heat, for the heat exchanger. The actual heat transfer coefficient is compared with a nominal or original heat transfer coefficient to determine if any deterioration in the coefficients has occurred which reflects the fouling of the heat exchanger. A simple ratio of the nominal to actual heat transfer coefficient is taken as a measure of this fouling factor.
U.S. Pat. No. 5,035,052 to Suzuki et al. discloses a method of assembling a heat exchanger including a method of determining values of parameters in a heat exchanger, and determining whether the efficiency of the heat exchanger is acceptable. The method includes determining the values of parameters: width of a louver formed in a fin of the heat exchanger, fin pitch, tilt angle of the fin, and tilt angle of the louver.
U.S. Pat. No. 5,177,975 to Mertens discloses apparatus for preparation of process water for presses.
U.S. Pat. No. 5,215,704 to Hirota discloses a method and apparatus for in situ testing of heat exchangers by measuring the heat transfer capabilities of an individual tube. A relatively small reservoir of service fluid is connected to the inlet and outlet ports of a tube. The reservoir is provided with a heater or chiller and the service fluid is circulated through the tube. When a steady state is reached, the heat transfer characteristics of the tube are measured using known mathematical relationships.
U.S. Pat. No. 5,318,009 to Zivalich, Jr. discloses a method and apparatus for emulating a perimeter induction unit air conditioning system.
U.S. Pat. Nos. 5,343,762 and 5,396,810 to Beulke disclose vortex flow meters for measuring fluid flow, each including a conduit having a wall surrounding a bore for carrying the fluid along a bore axis. A pivoting member moves in response to vortices in the fluid and extends from a hole in the wall into the bore, and sensing means is provided for sensing the motion of the pivoting member to provide an output indicative of flow.
U.S. Pat. No. 5,353,653 to Watanabe et al. discloses a heat exchanger abnormality monitoring system having heat-exchange tubes for heating feed water with extraction steam, an inlet and an outlet for the feed water, and a drain cooling zone, includes a process input, an apparatus for calculating the differential pressure between the feed water pressures at the inlet and outlet, an apparatus for computing the heat exchanging performance of the heat exchanger, and judgement apparatus for monitoring the differential pressure and the heat exchanging performance, thereby judging the presence or absence of scale accretion within the heat exchanger and, whenever scale accretion is present, judging the specific locations of the scale accretion in the inner and outer surfaces of the heat-exchange tubes, fluid flow distribution passageways, and devices other than the heat-exchange tubes.
U.S. Pat. No. 5,399,017 to Droege discloses a method for evaluating the type, extent, and threshold of fouling in a heat exchanger test tube by using a reference test block to measure a reference thermal relaxation time at a guaranteed clean reference section of a heat exchanger test tube and comparing the reference thermal relaxation time with thermal relaxation times measured at the bottom region of unclean sections of the heat exchanger test tube.
U.S. Pat. No. 5,828,712 to Laurent et al. discloses a coolant water flow rate test using a nonradioactive tracer agent in operation of a water-cooled nuclear fission reactor. U.S. Pat. No. 5,913,614 to Smith et al. discloses a recirculating plumbing system in which the dispensing temperature and flow of clean water are adjusted. U.S. Pat. No. 5,915,343 to Zenobi discloses a system for rapid cooling of engines on a test bench.
U.S. Pat. No. 5,927,400 to Bononi et al. discloses a device and method for the adjustment of the flow rate of a liquid which circulates within thermal convectors or heat exchangers making up part of heating, conditioning or ventilation plants, or apparatus for the thermal treatment of products. The device comprises a body within which a movable shutter is provided, the position of which allows for adjusting the quantity of liquid flowing between at least an inlet duct and an outlet duct, the positioning of the shutter being obtained by way of a suitable actuator. The device also comprises a control circuit and an instant flow rate and/or quantity meter of the liquid flowing in one of said ducts, for the automatic and continuous adjustment of the flow, by way of the appropriate positioning of the shutter.
U.S. Pat. No. 6,079,950 to Seneff discloses a pool recirculation control system for a swimming pool or spa. A temperature sensor supplies a signal to a controller to cause a pump to be operated for a longer period of time when the water temperature is above a predetermined threshold temperature, and to be operated for a shorter period of time when the water temperature is below the predetermined threshold.
U.S. Pat. No. 6,086,828 to Thompson discloses a method of heat exchanger efficiency control by differential temperature in which a regenerative thermal oxidizer includes a number of heat exchange columns topped by a combustion chamber. Contaminated air is directed into one of the columns and oxidation is completed as the flow passes through the combustion chamber. From the combustion chamber, the now clean air flows vertically downward through another column and then is directed via an outlet through an outlet manifold and released to atmosphere or recirculated back to the oxidizer. A combustible fuel is added to the contaminated air prior to its entry into one of the columns. The addition of the combustible fuel is regulated by continuously monitoring the inlet and outlet temperatures and comparing a difference between these temperatures to a predetermined value. Further control is achieved by measuring the flow of contaminated air to the oxidizer via pressure differential and coordinating that measurement with the temperature differential measurement.
The present invention is an apparatus for evaluating the heat removal capacity of chilled-coolant-recirculating systems, such as chilled-water-recirculating systems. The apparatus includes a heat load having an inlet and an outlet for coolant, a flow meter for measuring coolant flow rate, inlet and outlet thermometers for measuring temperatures of coolant at inlet and outlet, and a data recorder connected to the flow meter, inlet thermometer, and outlet thermometer for recording their data outputs, which are used for characterizing the coolant-recirculating heat exchanger system. The apparatus may also include an optional computer operable for calculating heat removal capacity. The computer may be connected to the data recorder, or the data recorder may be integral with the computer. A computer may also be used to aid in controlling various operating parameters.
The apparatus measures at least coolant flow rate and inlet coolant temperature and return (outlet) coolant temperature. It then calculates the amount of heat removed, using conventional energy-transfer equations. In addition to coolant flow rate and temperature measurements, the apparatus measures inlet and outlet pressure to determine pressure drop and pressure stability. Optionally, it may also measure one or more temperatures associated with equipment to be cooled, especially to ensure that any critical maximum temperatures are not exceeded. The apparatus enables users to monitor and control the efficiency of their heat exchangers. Monitoring and controlling flow rate and temperature can help users to maximize the efficiency of heat exchanger installations, potentially resulting in substantial energy savings over time. With the present apparatus, companies with chilled water systems can identify chilled water system capacity limitations vs. heat load requirements. This can result in major cost savings by avoiding system downtime caused by heat load and capacity imbalance.
In addition to the measuring instruments and the data logger, the apparatus includes a heat load emulator. This device is used with computer software to calculate heat loads from operational equipment or to analyze the heat load capacity of a chilled coolant system with multiple heat sources. The heat load emulator can be directly connected into a chilled-coolant-recirculating system as a heat load source while online equipment is being evaluated. Alternatively, the apparatus can be configured to generate data for chilled-coolant-recirculating system capacity before new or additional equipment is placed online.